Method of forming mark on anodized surface of aluminum object

ABSTRACT

A method to mark an aluminum object ( 1 ) includes the steps of: providing an aluminum substrate ( 10 ); anodizing and coloring the aluminum substrate; providing a mask ( 2 ) with a pattern ( 25 ) in the same shape as a mark ( 15 ) to be formed on the aluminum object; irradiating a portion of the anodized surface ( 12 ) of the aluminum substrate with an ultraviolet beam through the pattern until the desired mark is formed on the anodized surface. The color of the mark is lighter than the anodized surface of the aluminum object, or gradually changes to the color of the anodized surface of the aluminum object.

FIELD OF THE INVENTION

[0001] The present invention relates to a method of forming marks on anodized surfaces of metal objects, and particularly to a method of forming marks on anodized surfaces of aluminum objects.

BACKGROUND OF THE INVENTION

[0002] At present, the most widely used method of marking anodized surfaces of metal objects is to irradiate the anodized surfaces with a laser beam. The method, which is described in France Pat. NO. 2649628, is carried out by projecting a laser beam and passing the beam through a mask onto the anodized surface of the component. However, before projecting the laser beam, the anodized surface must be covered with a layer which does not offer any resistance to the laser and which is incompatible with the anodized surface. Adding the layer increases the cost of the process and the formed mark is not durable. The coloring of the formed mark tends to fade or bleed over time. Furthermore, the method described above is costly because it uses laser beams.

[0003] Therefore, an improved method of marking the anodized surface of a metal object that overcomes the above-mentioned disadvantages is desired.

SUMMARY OF THE INVENTION

[0004] A main object of the present invention is to provide a convenient and inexpensive method of forming a durable mark on an anodized surface of an aluminum object.

[0005] Another object of the present invention is to provide a method of forming a mark on an anodized surface of an aluminum object which mark gradually changes its color over a distance on the object to the color of the anodized surface of the aluminum object.

[0006] To achieve the above objects, a method for marking an aluminum object comprises the steps of: providing an aluminum substrate; anodizing and coloring said aluminum substrate; providing a mask with a pattern in the same shape as a mark to be formed on the aluminum substrate; irradiating the anodized surface of the aluminum substrate with an ultraviolet beam through said pattern of the mask, until the desired mark is formed thereon.

[0007] The method also can include a step of preparing the pattern of the mask to make the ultraviolet transmittance of the pattern non-uniform or to make the ultraviolet transmittance of the pattern gradually change, and after the irradiating step as described above, the formed mark is in different color or gradually changes its color to the color of the anodized surface of the aluminum object.

[0008] Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of a preferred embodiment thereof when taken in conjunction with the accompanying drawings, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a perspective view of an anodized, unmarked aluminum object before using a method of marking according to the present invention;

[0010]FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1;

[0011]FIG. 3 is a diagrammatic view showing the process according to the present invention of forming a mark on the anodized surface of the aluminum object of FIG. 1;

[0012]FIG. 4 is a perspective view of the anodized aluminum object after marking according to the method of the present invention; and

[0013]FIG. 5 is a cross-sectional enlarged view taken along line V-V of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

[0014] Referring now to the drawings in detail, FIGS. 1 and 2 show an object 1 to be marked. The object 1 comprises a substrate 10 and a colored anodic oxide film (or anodized surface) 12 on the substrate 10. The substrate 10 is made of aluminum or aluminum alloy and is manufactured by conventional methods such as extrusion. FIGS. 4 and 5 show the object 1 with a mark 15 on the anodic oxide film 12. The color of the mark 15 is lighter than the color of the anodic oxide film 12. FIG. 3 shows the process of forming the mark 15 on the object 1. The method of forming the mark 15 on the object 1 comprises the steps of: providing the substrate 10; anodizing and coloring said substrate 10; providing a mask 2 with a pattern 25 in the same shape as the mark 15 to be formed on the object 1; irradiating the anodized surface 12 with an ultraviolet beam 3 through the pattern 25 of the mask 2, onto the anodized surface 12 of the substrate 10, until the desired mark 15 is formed thereon.

[0015] In the anodizing step, the substrate 10 is first subjected to degreasing, washing, drying or other conventional pretreatments such as chemical-mechanical polishing, if necessary. Then, the substrate 10 is dipped into an electrolytic cell containing a sulfuric acid solution, and a direct current power is applied to the electrolytic cell. During the anodizing process, a concentration of the sulfuric acid in the electrolytic cell is in a range of 100 to 200 g/L, a voltage of the direct current power applied to the electrolytic cell is between 8 and 16 V, and a current density of the direct current power is between 100.0 and 200.0 A/m². The anodization is carried out for 30 to 60 minutes, therefore, the anodic oxide film 12 is formed on the surface of the substrate 10 and the thickness of the anodic oxide film 12 is in a range of 10 to 20 μm. After being anodized, the object 1 is washed, dried, and then soaked in a dyeing bath containing organic dyes to color the anodic oxide film 12. A concentration of the organic dyes is between 1 to 10 g/L. The dyeing process is performed for 5 to 20 minutes. The organic dyes comprise aluminum red GLW and aluminum violet CLW, so that the color of the anodized surface 12 of the substrate 10 is red.

[0016] Other organic dyes can be used to get other desired colors of the anodized surface 12 of the substrate 10.

[0017] Other conventional coloring methods such as electrolytic coloring, integral coloring, or inorganic dye coloring can be used to color the anodic oxide film 12.

[0018]FIG. 3 shows a process of forming the mark 15 on the object 1 using an ultraviolet beam 3 irradiating the anodized surface 12 of the object 1. The mask 2 shown in FIG. 3 includes the pattern 25 thereon. The pattern 25 has the same shape as the mark 15 to be formed on the object 1. The mask 2 is covered with a coating on all areas except for the area defining the pattern 25. The coating comprises an ultraviolet absorbing compound for inhibiting ultraviolet light transmission therethrough. Therefore, the ultraviolet beam 3 can only be transmitted through the pattern 25. When the ultraviolet beam 3 irradiates a portion of the anodized surface 12 through the pattern 25, the organic dyes in the irradiated area of the anodic oxide film 12 are partly decomposed, the color of the irradiated area fades, and the mark 15 is formed. Thus, the color of the mark 15 is lighter than the anodized surface 12 of the object 1.

[0019] If the pattern 25 of the mask 2 is designed to have different ultraviolet transmittance in different areas, the formed mark 15 has different shades of color in different areas.

[0020] If the ultraviolet transmittance of the pattern 25 is gradually changed over a distance on the mark 2, the formed mark 15 gradually changes its color to the color of the anodized surface 12.

[0021] It is understood that the invention may be embodied in other forms without departing from the spirit thereof. Thus, the present examples and embodiment are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. 

What is claimed is:
 1. A method for marking an aluminum object comprising the steps of: providing an aluminum substrate; anodizing and coloring said aluminum substrate; providing a mask with a pattern in the same shape as a mark to be formed on the aluminum object; irradiating a portion of the anodized surface of said aluminum substrate with an ultraviolet beam through said pattern until the desired mark is formed on the anodized surface.
 2. The method as claimed in claim 1, wherein the colorizing process is electrolytic coloring, dye coloring or integral coloring.
 3. The method as claimed in claim 1, wherein the mask is covered with a coating on all areas except for the area defining the pattern and the coating comprises an ultraviolet absorbing compound for inhibiting transmission of ultraviolet light therethrough.
 4. The method as claimed in claim 3, wherein the ultraviolet beam can only be transmitted through the pattern.
 5. The method as claimed in claim 4, wherein the color of the mark is lighter than the anodized surface of the aluminum object.
 6. The method as claimed in claim 5, wherein the pattern of the mask has different ultraviolet transmittance in different areas.
 7. The method as claimed in claim 6, wherein the mark has different shades of color in different areas.
 8. The method as claimed in claim 7, wherein the ultraviolet transmittance of the pattern gradually changes.
 9. The method as claimed in claim 8, wherein the color of the mark gradually changes to the color of the anodized surface.
 10. A method for marking an aluminum object comprising the steps of: providing an aluminum substrate; anodizing and coloring said aluminum substrate; providing a mask with a pattern, the mask being covered with a coating comprising an ultraviolet absorbing compound for inhibiting ultraviolet light from being transmitted therethrough on all areas except for the area defining the pattern; irradiating a portion of the anodized surface of said aluminum substrate with an ultraviolet beam through said pattern until the desired mark is formed on the anodized surface.
 11. The method as claimed in claim 10, wherein the colorizing process is electrolytic coloring, dye coloring or integral coloring.
 12. The method as claimed in claim 10, wherein the pattern has the same shape as the desired mark.
 13. The method as claimed in claim 12, wherein the ultraviolet beam can only be transmitted through the pattern.
 14. The method as claimed in claim 13, wherein the ultraviolet transmittance of the pattern gradually changes.
 15. The method as claimed in claim 14, wherein the color of the mark gradually changes to the color of the anodized surface.
 16. A method of marking an aluminum object comprising steps of: providing an aluminum substrate; anodizing and coloring said aluminum substrate to have color absorbed in a final formed anodized layer; and decolorizing said anodized layer in a pattern while without jeopardizing/thinning said anodized layer.
 17. The method as claimed in claim 16, wherein the step of decolorizing is performed via irradiation.
 18. The method as claimed in claim 16, wherein said pattern is defined by a mask.
 19. The method as claimed in claim 17, wherein the decolorizing performs different degrees depending upon time and strength of said irradiation. 